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AIP conference proceedings

Quantum Key Distribution with Polarization-Entangled Multiphotons

Yu‐Hui Luo

Published Jan 1, 2004• 0 citations
Publisher

Abstract

Multiphoton entanglement in the same polarization has been theoretically shown to be obtainable by type‐I spontaneous parametric down‐conversion (SPDC), which can generate bright pulses more easily than type‐II SPDC. A new quantum cryptographic protocol utilizing polarization pairs with the detected type‐I entangled multiphotons is proposed as quantum key distribution. The information capacity versus photon number corresponding to polarization is calculated after considering the transmission loss inside the optical fiber, the detector efficiency and intercept‐resend attacks under the level of channel error. This result thus achieved compares very favorably with all other schemes employing entanglement.

DOI
10.1063/1.1834440

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Multiphoton entanglement in the same polarization has been theoretically shown to be obtainable by type‐I spontaneous parametric down‐conversion (SPDC), which can generate bright pulses more easily than type‐II SPDC. A new quantum cryptographic protocol utilizing polarization pairs with the detected type‐I entangled multiphotons is proposed as quantum key distribution. The information capacity versus photon number corresponding to polarization is calculated after considering the transmission loss inside the optical fiber, the detector efficiency and intercept‐resend attacks under the level of channel error. This result thus achieved compares very favorably with all other schemes employing entanglement.
Multiphoton entanglement in the same polarization has been shown theoretically to be obtainable by type-I spontaneous parametric downconversion (SPDC), which can generate bright pulses more easily than type-II SPDC. A new quantum cryptographic protocol utilizing polarization pairs with the detected type-I entangled multiphotons is proposed as quantum key distribution. We calculate the information capacity versus photon number corresponding to polarization after considering the transmission loss inside the optical fiber, the detector efficiency, and intercept-resend attacks at the level of channel error. The result compares favorably with all other schemes employing entanglement.
Multiphoton entanglement in the same polarization has been theoretically shown to be obtainable by type-I spontaneous parametric down-conversion (SPDC), which can generate bright pulses more easily than type-II SPDC. A quantum cryptographic protocol utilizing photon number coding of the detected type-I entangled multiphotons is described. The information capacity versus photon number is calculated after considering the transmission loss inside the optical fiber and the detector efficiency, considering possible attacks to the scheme. The result thus achieved compares very favorably with all other schemes employing entanglement.
A new scheme for quantum cryptography, based on a distributed polarization quantum intensity interferometer, is presented. Two-photon entangled states generated via the optical nonlinear process of type-II phase-matched spontaneous parametric down-conversion are used to securely distribute secret cryptographic keys. The high contrast and stability of the quantum interference pattern obtained by using this design renders it superior to the best existing single-photon polarization technique. In addition, the use of high-repetition-rate femtosecond pump pulses for down-conversion significantly enhances the production rate of entangled photon pairs for key distribution.
Abstract Multiphoton entanglement is the basis of many quantum communication schemes, quantum cryptographic protocols, and fundamental tests of quantum theory. Spontaneous parametric down‐conversion is the most effective source for polarization entangled photon pairs. Here we show, that a class of entangled 4‐photon states can be directly created by parametric down‐conversion. These states exhibit perfect quantum correlations and a high robustness of entanglement against photon loss. Therefore these states are well suited for new types of quantum communication.
We theoretically analyze the feasibility of entanglement-based quantum key distribution (QKD) protocols [1], [2], considering both spontaneous parametric down-conversion (SPDC) and quantum dot (QD) sources. We account for multiphoton emission in SPDC sources and fine-structure splitting (FSS) in QD. In addition, we incorporate imperfect detection, including dark counts and limited efficiency. For SPDC sources, we confirm the presence of vacuum and multiphoton pairs renders them unsuitable for secure device-independent (DI) QKD implementations. Conversely, with QD sources, accounting for the effects of FSS results in reduced secret key rates compared to ideal conditions. Our findings are crucial for the practical implementation of entanglement-based QKD protocols using realistic sources and detectors.
We propose an efficient quantum key distribution protocol based on the photon-pair generation from parametric down-conversion (PDC). It uses the same experimental setup as the conventional protocol, but a refined data analysis enables detection of photon-number splitting attacks by utilizing information from a built-in decoy state. Assuming the use of practical detectors, we analyze the unconditional security of the new scheme and show that it improves the secure key generation rate by several orders of magnitude at long distances, using a high intensity PDC source.